A typical example of such type of product feeding device is disclosed in the Japanese utility model opening gazette No. 59-52426. The cited device includes a conical dispersion table which is rotationally driven with vertical vibration and a plurality of radial vibratory conveyer troughs and corresponding retaining hoppers disposed respectively above the weighing hoppers. In operation of this device, product to be weighed, which is fed down onto the apex of the dispersion table, slips down the conical surface towards the periphery and falls into each radial conveyer trough. Each trough is subjected to linear vibration to convey the product into the corresponding retaining hopper. Each retaining hopper is provided with means for detecting the amount of product fed thereto and providing a signal to stop the feed of product when a predetermined amount is reached.
In order to obtain high accuracy of combined weight in the combination weighing machine, it is preferable that the weights of product in respective weighing hoppers exhibit suitable variance. In order to achieve such variance, the amount of product received each weighing hopper from the corresponding retaining hopper is preferably controlled as described above.
While, in such prior art product feeding devices as cited above, the vibration of each radial conveyer trough is controlled for controlling the amount of feed, such troughs result in a large overall diameter of the feeding device and, therefore, in a large size of the combination weighing machine occupying a large space for installation. Such a large size of the machine results in elongated product collection paths which, in turn, results in an increased collection time and reduced efficiency of the machine.
Accordingly, an object of this invention is to provide an improved product feeding device having a significantly reduced diameter, thereby enabling a reduction in the size of the combination weighing machine and an increase in the machine's efficiency or the rate of delivery.
This object can be attained in accordance with the present invention by removing the radial conveyer troughs from the prior art product feeding device and, instead, providing each retaining hopper with a novel device for controlling the amount of product ultimately fed to the corresponding weighing hopper.